Electronic Device, System And Method For Insulation Resistance Measurements With Functions Of Self-Diagnosis And Diagnosis Of Insulation Loss With Respect To Ground Of An Energized Electrical Apparatus

ABSTRACT

A vehicle step apparatus including an extending and retracting device having a mounting bracket, a step bracket, and an arm assembly. A gear box has a cavity into which at least a portion of a motor shaft of a motor is inserted. A worm wheel is rotatably disposed in the cavity and has a worm wheel body meshing with the motor shaft. An output shaft is mounted to the worm wheel body. A sun gear is fitted over the output shaft. A planet carrier is rotatably disposed in the cavity and connected with the arm assembly. A planet gear is rotatably mounted to the planet carrier and meshes with the sun gear. An adjusting member is mounted in the gear box, and is movable in an axial direction of the motor shaft and abuts against a free end of the motor shaft.

RELATED APPLICATIONS

This application claims priority and benefits of Chinese Patent Application No. 201510469324.4, filed with State Intellectual Property Office on Aug. 4, 2015, Chinese Patent Application No. 201520580148.7, filed with State Intellectual Property Office on Aug. 4, 2015, Chinese Patent Application No. 201510468824.6, filed with State Intellectual Property Office on Aug. 4, 2015, Chinese Patent Application No. 201520576675.0, filed with State Intellectual Property Office on Aug. 4, 2015, Chinese Patent Application No. 201510962062.5, filed with State Intellectual Property Office on Dec. 21, 2015, and Chinese Patent Application No. 201521076768.3, filed with State Intellectual Property Office on Dec. 21, 2015, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to a field of vehicle technology, and more particularly, to a vehicle step apparatus and a motor assembly thereof.

2. Description of the Related Art

A vehicle step apparatus mounted on a chassis of a vehicle is used to assist passengers to get on or off the vehicle. An extending and retracting device of the vehicle step apparatus is driven by a motor via a reducing mechanism. Because a mounting space of the vehicle step apparatus is limited, it is required that the vehicle step apparatus has a small size. There are two kinds of reducing mechanisms for the current vehicle step apparatus.

The first kind of reducing mechanism is a combination of a worm-and-worm wheel reducing mechanism and a cylindrical gear reducing mechanism. The first kind of reducing mechanism has defects of a low protection level and a large size, and thus is difficult to be mounted on a vehicle body.

The second kind of reducing mechanism is a combination of a worm-and-worm wheel reducing mechanism and another worm-and-worm wheel reducing mechanism. The second kind of reducing mechanism has defects of a high manufacture cost and a large size, and thus is difficult to be manufactured and to be mounted on the vehicle body.

Moreover, because a worm of the reducing mechanism has a great axial force, an axial gap of the worm increases after a period of usage and due to abrasion caused therein, so that the transmission efficiency is decreased, and the noise during reversal is increased.

SUMMARY OF THE INVENTION

The present invention seeks to solve at least one of the technical problems existing in the related art. Therefore, embodiments of the present invention provide a vehicle step apparatus. The vehicle step apparatus according to embodiments of the present invention has advantages of high transmission efficiency, low noise during reversal, a compact structure, and a small size.

Embodiments of a first aspect of the present invention provide a vehicle step apparatus. The vehicle step apparatus includes an extending and retracting device comprising a mounting bracket, a step bracket, and an arm assembly connected between the mounting bracket and the step bracket to drive the step bracket to move between an extending position and a retracting position. A step is mounted on the step bracket and a motor has a motor shaft including a worm. A gear box defines a cavity therein. At least a portion of the motor shaft is inserted into the cavity. A worm wheel is rotatably disposed in the cavity, and includes a worm wheel body meshing with the motor shaft and an output shaft mounted to the worm wheel body. A sun gear is fitted over the output shaft. A planet carrier is rotatably disposed in the cavity and connected with the arm assembly to drive the arm assembly. A planet gear is rotatably mounted to the planet carrier and meshes with the sun gear. An adjusting member is mounted in the gear box, and is movable in an axial direction of the motor shaft and abuts against a free end of the motor shaft.

Embodiments of a second aspect of the present invention provide a motor assembly of a vehicle step apparatus. The motor assembly of a vehicle step apparatus includes a motor having a motor shaft including a worm. A gear box defines a cavity therein. At least a portion of the motor shaft is inserted into the cavity. A worm wheel is rotatably disposed in the cavity, and has a worm wheel body meshing with the motor shaft, and an output shaft mounted to the worm wheel body. A sun gear is fitted over the output shaft. A planet carrier is rotatably disposed in the cavity and connected with the arm assembly to drive the arm assembly. A planet gear is rotatably mounted to the planet carrier and meshes with the sun gear. An adjusting member is mounted in the gear box, and is movable in an axial direction of the motor shaft and abuts against a free end of the motor shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic view of a vehicle step apparatus according to an embodiment of the present invention, in which a step bracket is in an extending position;

FIG. 2 is a schematic view of a vehicle step apparatus according to an embodiment of the present invention, in which a step bracket is in a retracting position;

FIG. 3 is a schematic view of a motor assembly of a vehicle step apparatus according to an embodiment of the present invention;

FIG. 4 is a sectional view of the motor assembly taken along line A-A in FIG. 3;

FIG. 5 is a schematic view of a motor assembly of a vehicle step apparatus according to an embodiment of the present invention;

FIG. 6 is an enlarged view of portion B in FIG. 5;

FIG. 7 is a schematic view of a motor assembly of a vehicle step apparatus according to an embodiment of the present invention;

FIG. 8 is an enlarged view of portion C in FIG. 7;

FIG. 9 is an exploded view of a vehicle step apparatus according to an embodiment of the present invention; and

FIG. 10 is a partially exploded view of a vehicle step apparatus according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will be made in detail to embodiments of the present invention. Embodiments of the present invention will be shown in drawings, in which the same or similar members and the members having same or similar functions are denoted by like reference numerals throughout the descriptions. The embodiments described herein according to drawings are explanatory and illustrative, not construed to limit the present invention.

In the specification, unless specified or limited otherwise, relative terms such as “central”, “longitudinal”, “lateral”, “front”, “rear”, “right”, “left”, “inner”, “outer”, “lower”, “upper”, “horizontal”, “vertical”, “above”, “below”, “up”, “top”, “bottom”, “inner”, “outer”, “clockwise”, “anticlockwise”, “axial”, “radial”, “circumferential” as well as derivative thereof (e.g., “horizontally”, “downwardly”, “upwardly”, etc.) should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of description and do not require that the present invention be constructed or operated in a particular orientation.

In addition, terms such as “first” and “second” are used herein for purposes of description and are not intended to indicate or imply relative importance or significance. Thus, features limited by “first” and “second” are intended to indicate or imply including one or more than one these features. In the description of the present invention, “a plurality of” relates to two or more than two.

In the description of the present invention, unless specified or limited otherwise, it should be noted that, terms “mounted”, “connected” and “coupled” may be understood broadly, such as permanent connection or detachable connection, electronic connection or mechanical connection, direct connection or indirect connection via intermediary, inner communication or interreaction between two elements. These having ordinary skills in the art should understand the specific meanings in the present invention according to specific situations.

In the description of the present invention, a structure in which a first feature is “on” a second feature may include an embodiment in which the first feature directly contacts the second feature, and may also include an embodiment in which an additional feature is formed between the first feature and the second feature so that the first feature does not directly contact the second feature, unless otherwise specified. Furthermore, a first feature “on”, “above” or “on top of” a second feature may include an embodiment in which the first feature is right “on,” “above”, or “on top of” the second feature, and may also include an embodiment in which the first feature is not right “on”, “above”, or “on top of” the second feature, or just means that the first feature has a sea level elevation larger than the sea level elevation of the second feature. While first feature “beneath”, “below” or “on bottom of” a second feature may include an embodiment in which the first feature is right “beneath”, “below” or “on bottom of” the second feature, and may also include an embodiment in which the first feature is not right “beneath”, “below” or “on bottom of” the second feature, or just means that the first feature has a sea level elevation smaller than the sea level elevation of the second feature.

A vehicle step apparatus 10 according to embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1 to FIG. 10, the vehicle step apparatus 10 according to embodiments of the present invention includes an extending and retracting device 101, a step 102, a motor 103, a gear box 104, a worm wheel 105, a sun gear 1061, a planet carrier 1062, a planet gear 1063 and an adjusting member 107.

The extending and retracting device 101 includes a mounting bracket 1011, a step bracket 1012 and an arm assembly 1013. The arm assembly 1013 is connected between the mounting bracket 1011 and the step bracket 1012, and drives the step bracket 1012 to move between an extending position and a retracting position. The step 102 is mounted on the step bracket 1012.

The motor 103 has a motor shaft 1031 configured as a worm. In other words, a helical tooth is formed in at least a portion of the motor shaft 1031. The gear box 104 has a cavity 1041 therein, and at least a portion of the motor shaft 1031 is inserted into the cavity 1041. The adjusting member 107 is mounted in the gear box 104, movable in an axial direction of the motor shaft 1031 and abuts against a free end of the motor shaft 1031.

The worm wheel 105 is rotatably disposed in the cavity 1041, and includes a worm wheel body 1051 and an output shaft 1052. The worm wheel body 1051 meshes with the motor shaft 1031, and the output shaft 1052 is mounted to the worm wheel body 1051. The sun gear 1061 is fitted over the output shaft 1052.

The planet carrier 1062 is rotatably disposed in the cavity 1041 and connected with the arm assembly 1013 to drive the arm assembly 1013, further to drive the step bracket 1012 to move between the extending position and the retracting position. The planet gear 1063 is rotatably mounted to the planet carrier 1062 and meshes with the sun gear 1061.

Operations of the vehicle step apparatus 10 according to embodiments of the present invention will be described with reference to FIG. 1 to FIG. 10. When the vehicle step apparatus 10 is not used by a user, the step bracket 1012 is in the retracting position.

When the user gets on the vehicle or gets off the vehicle, the motor shaft 1031 of the motor 103 rotates clockwise (or counterclockwise), and drives the worm wheel body 1051 and the output shaft 1052 mounted to the worm wheel body 1051 to rotate. Because the sun gear 1061 is fitted over the output shaft 1052, the output shaft 1052 drives the sun gear 1061 to rotate.

The sun gear 1061, the planet gear 1063 and the planet carrier 1062 constitute a planetary gear reducing mechanism, the power is output by the planet carrier 1062. Specifically, the planet carrier 1062 is connected with the arm assembly 1013 so as to drive the step bracket 1012 to move from the retracting position to the extending position via the arm assembly 1013. That is to say, the step 102 is moved from the retracting position to the extending position, so that it is convenient for the user to get on the vehicle or get off the vehicle by treading on the step 102.

After the user gets on the vehicle or gets off the vehicle, the motor shaft 1031 of the motor 103 rotates counterclockwise (or clockwise) so as to drive the step bracket 1012 to move from the extending position to the retracting position.

The vehicle step apparatus 10 according to embodiments of the present invention has a reverse self-locking function by providing a worm-and-worm wheel mechanism, so as to protect the extending and retracting device 101.

By providing the planetary gear reducing mechanism, the vehicle step apparatus 10 according to embodiments of the present invention can achieve a desired reduction ratio, and has a smaller size and more compact structure compared with a cylindrical gear reducing mechanism and a worm-and-worm wheel reducing mechanism. Thus, the vehicle step apparatus 10 is more suitable to be mounted at a bottom of the vehicle, in which the bottom of the vehicle has a narrow space.

Moreover, because the motor shaft 1031 (i.e. a worm) of the motor 103 has a great axial force, an axial gap of the motor shaft 1031 increases after a period of usage and due to abrasion caused therein, so that the transmission efficiency is decreased, and the noise during reversal is increased.

However, in embodiments of the present invention, by providing the adjusting member 107 in the gear box 104, which is movable in the axial direction of the motor shaft 1031 and abuts against the free end of the motor shaft 1031, the axial gap of the motor shaft 1031 can be adjusted by moving the adjusting member 107 along the axial direction of the motor shaft 1031.

That is to say, the axial gap of the motor shaft 1031 can be eliminated by moving the adjusting member 107 along the axial direction of the motor shaft 1031, so as to improve the transmission efficiency and decrease the noise during reversal.

Thus, the vehicle step apparatus 10 according to embodiments of the present invention has advantages of high transmission efficiency, low noise during reversal, a compact structure, a small size, high safety, high reliability, a long working life, a low manufacture cost and so on, and is suitable to be mounted at the bottom of the vehicle, in which the bottom of the vehicle has the narrow space.

As shown in FIG. 1 to FIG. 10, in some embodiments, the vehicle step apparatus 10 includes the extending and retracting device 101, the step 102 and a motor assembly. The motor assembly includes the motor 103, the gear box 104, the worm wheel 105, the sun gear 1061, the planet carrier 1062, the planet gear 1063 and the adjusting member 107.

As shown in FIG. 4, the gear box 104 includes a box body 1042, a first cover 1043 and a second cover 1044. The box body 1042 has the cavity 1041 therein, and the cavity 1041 has an open first end (i.e., an open lower end) and an open second end (i.e., an open upper end) opposite to the first end. The first cover 1043 is mounted on the box body 1042 and covers the first end of the cavity 1041. The second cover 1044 is mounted on the box body 1042 and covers the second end of the cavity 1041.

A first seal ring 10451 is disposed between the box body 1042 and the first cover 1043, and a second seal ring 10452 is disposed between the box body 1042 and the second cover 1044. Thus, the gear box 104 has a more reasonable structure. Moreover, a sealing performance of the gear box 104 can be improved by disposing the first seal ring 10451 between the box body 1042 and the first cover 1043 and disposing the second seal ring 10452 between the box body 1042 and the second cover 1044, so as to prevent external impurities (such as water, sand and soil) from entering the cavity 1041 and further to prevent parts disposed in the cavity 1041 from being damaged.

Consequently, a waterproof performance and a protection level of the motor assembly can be greatly improved, so as to enhance reliability and a working life of the motor assembly in harsh environments. The motor assembly can achieve an IP68 protection level, and thus the vehicle step apparatus 10 and the motor assembly thereof can be used in various kinds of harsh environments, for example river, muddy road, field road, mountain road and so on, so that an application scope and an operation condition of the vehicle step apparatus 10 and the motor assembly thereof are expanded.

An up and down direction is denoted by arrow D in FIG. 4. The up and down direction denoted in FIG. 4 is a predetermined direction so as to describe the vehicle step apparatus 10 and the motor assembly thereof conveniently and may be different from a real up and down direction in the real space.

As shown in FIG. 4, the gear box 104 further includes a mounting stand 1047, and the mounting stand 1047 includes a first annular part 10471 and a second annular part 10472. The first annular part 10471 has an outer edge, and the outer edge of the first annular part 10471 is connected with a wall of the cavity 1041. The second annular part 10472 has a lower edge, and the lower edge of the second annular part 10472 is connected with an inner edge of the first annular part 10471.

Specifically, the second annular part 10472 is disposed in the up and down direction, and the first annular part 10471 is perpendicular to the second annular part 10472.

The second annular part 10472 is fitted over the output shaft 1052, and the worm wheel body 1051 is fitted over the second annular part 10472. The sun gear 1061 is fitted over a portion of the output shaft 1052, and the portion of the output shaft 1052 is below the first annular part 10471 and the second annular part 10472.

It is convenient for both the worm wheel body 1051 and the output shaft 1052 to be steadily mounted by providing the mounting stand 1047. Advantageously, the box body 1042 is integral with the mounting stand 1047. An inner and outer direction is denoted by arrow E in FIG. 4.

As shown in FIG. 4, the gear box 104 further includes a supporting boss 1048, and the supporting boss 1048 has a circular shape and is disposed on an upper surface of the first annular part 10471. The supporting boss 1048 has a center axis coinciding with a center axis of the output shaft 1052. The worm wheel body 1051 is disposed on the supporting boss 1048. Thus, a friction area between the worm wheel body 1051 and the first annular part 10471 is decreased.

In an embodiment of the present invention, as shown in FIG. 4, a bearing 1049 is disposed between the second annular part 10472 and the output shaft 1052. In other words, the bearing 1049 is disposed in the second annular part 10472, and the bearing 1049 is fitted over the output shaft 1052. That is to say, the second annular part 10472 is fitted over the bearing 1049. Thus, a friction force between the second annular part 10472 and the output shaft 1052 is decreased remarkably.

Advantageously, a first groove is formed in one of an inner circumferential surface of the second annular part 10472 and an outer circumferential surface of the bearing 1049, a bulge 10473 is disposed on the other of the inner circumferential surface of the second annular part 10472 and the outer circumferential surface of the bearing 1049, and the bulge 10473 is fitted within the first groove.

As shown in FIG. 4, FIG. 9 and FIG. 10, the planet carrier 1062 is connected with the arm assembly 1013 via a connecting shaft 1064. Specifically, a through hole 10431 is formed in the first cover 1043, and a first portion of the planet carrier 1062 is fitted within the through hole 10431. A third seal ring 10453 is disposed between the first portion of the planet carrier 1062 and a wall of the through hole 10431. A mounting hole 10621 is formed in the first portion of the planet carrier 1062, specifically in a lower surface of the first portion, and an end of the connecting shaft 1064 is fitted within the mounting hole 10621.

Moreover, the sealing performance of the gear box 104 can be improved by disposing the third seal ring 10453 between the first portion of the planet carrier 1062 and the wall of the through hole 10431, so as to prevent the external impurities (such as water, sand, and soil) from entering the cavity 1041 and further to prevent the parts disposed in the cavity 1041 from being damaged.

The waterproof performance and the protection level of the motor assembly can be improved, so as to enhance the reliability and the working life of the motor assembly in harsh environments. The motor assembly can achieve the IP68 protection level, and thus the vehicle step apparatus 10 and the motor assembly thereof can be used in various kinds of harsh environments, for example river, muddy road, field road, mountain road and so on, so that the application scope and the operation condition of the vehicle step apparatus 10 and the motor assembly thereof are expanded.

As shown in FIG. 4 to FIG. 8, in some embodiments of the present invention, a threaded hole 1046 is formed in the gear box 104, and the adjusting member 107 is fitted within the threaded hole 1046 via thread connection. Therefore, the adjusting member 107 can be rotated to abut against the free end of the motor shaft 103 when the axial gap of the motor shaft 1031 is increased, so that the axial gap of the motor shaft 1031 can be eliminated.

In an embodiment of the present invention, a second groove 1071 is formed in an end surface, which is far away from the motor shaft 1031, of the adjusting member 107. Thus, the adjusting member 107 can be rotated by a screwdriver inserted into the second groove 1071. Specifically, the adjusting member 107 may be a nut.

As shown in FIG. 9 and FIG. 10, the vehicle step apparatus 10 further includes an elastic member 108. The elastic member 108 elastically deforms so as to store energy when the motor 103 drives the step bracket 1012 to move towards the extending position, and to release energy so as to assist the motor 103 to drive the extending and retracting device 101 when the motor 103 drives the step bracket 1012 to move towards the retracting position.

When the motor shaft 1031 rotates clockwise (or counterclockwise), the motor shaft 1031 drives the elastic member 108 to move and makes the elastic member 108 elastically deformed so as to store energy, and the step 102 is moved from the retracting position to the extending position.

When the motor shaft 1031 rotates counterclockwise (or clockwise), the elastic member 108 restores and releases energy so as to assist the motor 103 to drive the extending and retracting device 101 to retract. Consequently, both a load and an operating current of the motor 103 are decreased when the motor shaft 1031 rotates counterclockwise (or clockwise), so that the operating current of the motor 103 in a process of driving the extending and retracting device 101 to extend approximately equals the operating current of the motor 103 in a process of driving the extending and retracting device 101 to retract, thus effectively protecting the motor 103 and prolonging the working life of the motor 103.

More specifically, the mounting bracket 1011 is mounted on a vehicle body of the vehicle, for example, the mounting bracket 1011 is mounted on a chassis of the vehicle. At least one arm of the arm assembly 1013 is pivotably connected with the mounting bracket 1011, and at least one arm of the arm assembly 1013 is pivotably connected with the step bracket 1012.

The connecting shaft 1064 is connected with an arm of the arm assembly 1013 so as to drive the arm assembly 1013 to move, and thus to drive the step bracket 1012 connected with the arm assembly 1013 to move.

In other words, the motor shaft 1031 drives the arm assembly 1013 to move via the connecting shaft 1064. Thus, the motor 103 can drive the extending and retracting device 101 to extend and retract by rotating clockwise and counterclockwise respectively.

Further, the elastic member 108 includes a scroll spring. The scroll spring has a first end 1081 and a second end 1082. The first end 1081 of the scroll spring is fixed, and the second end 1082 of the scroll spring is driven by the motor shaft 1031 so as to twist.

Specifically, as shown in FIG. 9 and FIG. 10, the elastic member 108 is a scroll spring. An end of an outermost ring of the scroll spring is bent outwards so as to form the first end 1081, and an end of an innermost ring of the scroll spring is bent inwards so as to form the second end 1082. Thus, the first end 1081 includes the end of the outermost ring of the scroll spring and a portion of the outermost ring which is connected with the end of the outermost ring, and the second end 1082 includes the end of the innermost ring of the scroll spring and a portion of the innermost ring which is connected with the end of the innermost ring.

When the extending and retracting device 101 is extended, i.e. when the step 102 is extended, the first end 1081 of the scroll spring is fixed, and the second end 1082 of the scroll spring rotates along with the motor shaft 1031 and thus is tightly twisted to store energy.

When the extending and retracting device 101 is retracted, i.e. when the step 102 is retracted, the first end 1081 of the scroll spring is fixed, and the second end 1082 of the scroll spring rotates along with the motor shaft 1031 so as to restore and release energy, thus assisting in driving the extending and retracting device 101 to retract. In addition, by adopting the scroll spring, the elastic member 108 has a simple and compact structure, and is easy to mount.

Additionally, the present invention is not limited to this, and the elastic member 108 may be an elastic sheet, a disc spring or another member capable of being elastically deformed.

Furthermore, those skilled in the related art may choose a suitable scroll spring based on a difference between the load of the motor 103 in the process of driving the step 102 to extend and the load of the motor 103 in the process of driving the step 102 to retract, so that the load of the motor 103 in the process of driving the step 102 to extend and the load of the motor 103 in the process of driving the step 102 to retract can be better balanced by the scroll spring.

As shown in FIG. 9 and FIG. 10, in an embodiment of the present invention, the vehicle step apparatus 10 further includes a cover 1092 and a connecting plate 1091. A recess is formed in the first cover 1043 of the gear box 104, and the cover 1092 covers the recess to define an accommodating space. The connecting plate 1091 is mounted in the accommodating space and driven by the motor shaft 1031 to rotate. The scroll spring is mounted within the accommodating space, the first end 1081 of the scroll spring is fixed in the cover 1092, and the second end 1082 of the scroll spring is connected with the connecting plate 1091.

Specifically, the connecting plate 1091 is a substantially circular plate. The connecting plate 1091 is disposed in the accommodating space, and has a first end surface opposite to the recess and a second end surface opposite to the cover 1092. The connecting plate 1091 is indirectly connected with the motor shaft 1031 (as the connecting plate 1091 may be directly connected with the connecting shaft 1064 which is indirectly connected with the motor shaft 1031) and is driven by the motor shaft 1031 to rotate.

The scroll spring is fitted over the connecting plate 1091, and the second end 1082 of the scroll spring is connected with the connecting plate 1091 and rotates along with the connecting plate 1091 in a same direction.

Thus, since the scroll spring is integrated in the motor assembly of the vehicle step apparatus 10, a transmission loss is decreased and the vehicle step apparatus 10 has a more compact entire structure.

As shown in FIG. 9 and FIG. 10, in some embodiments, the cover 1092 is detachably fastened to the first cover 1043 of the gear box 104.

A position limiting notch 10921 is formed in the cover 1092, a position limiting column 10111 is formed on the mounting bracket 1011, and the position limiting column 10111 is fitted in the position limiting notch 10921 to mount the cover 1092 to the mounting bracket 1011. The first end 1081 of the scroll spring is fitted over the position limiting column 10111.

As shown in FIG. 9 and FIG. 10, the recess is formed in an end surface, which is facing the mounting bracket 1011, of the first cover 1043 of the gear box 104. The cover 1092 includes a cover body and a flange connected with an edge of the cover body. An inner wall of the flange has a stepped positioning surface, and the cover 1092 covers the recess via the stepped positioning surface. The position limiting notch 10921 extends inwards from an edge of the cover 1092.

The position limiting column 10111 is formed on a side surface of the mounting bracket 1011 opposite to the gear box 104, and a clamping groove fitted with the position limiting notch 10921 is formed in the position limiting column 10111. Specifically, two position limiting columns 10111 are provided, and bottom surfaces of the clamping grooves of the two position limiting columns 10111 force the cover 1092 to abut against the first cover 1043 of the gear box 104, so as to limit a position of the cover 1092 in the axial direction. Side surfaces of the clamping grooves of the two position limiting columns 10111 limit the position of the cover 1092 in both a radial direction and a circumferential direction. The first end 1081 of the scroll spring extends out of the position limiting notch 10921 and is fitted over the position limiting column 10111.

Thus, the cover 1092, the first cover 1043 of the gear box 104 and the mounting bracket 1011 are fixedly connected together, and a suitable position is provided to fix the first end 1081 of the scroll spring, so that a torsional deformation of the scroll spring is decreased during mounting and using thereof.

It may be understood by those skilled in the related art that the cover 1092, the connecting plate 1091 and the recess each may have a circular shape, an oval shape and so on. The number of the position limiting notches 10921 and the number of the position limiting columns 10111 each is not limited to two, and when the number of the position limiting notches 10921 is more than two, the multiple position limiting notches 10921 are evenly arranged and spaced apart from one other along a circumferential direction of the cover 1092.

Advantageously, an inserting slot 10911 is formed in an outer circumferential surface of the connecting plate 1091, and the second end 1082 of the scroll spring is inserted into and fitted within the inserting slot 10911.

As shown in FIG. 9 and FIG. 10, the inserting slot 10911 extends inwards from an outer edge of the connecting plate 1091, and the inserting slot 10911 extends along a radial direction of the connecting plate 1091.

A center of the connecting plate 1091 has a spline hole, and the connecting shaft 1064 has an external spline, so that the connecting plate 1091 can be fitted over and connected with the connecting shaft 1064 by a spline fit between the spline hole and the external spline, thereby ensuring the power transmission and providing convenient assembling and disassembling. Further, the connecting shaft 1064 is connected with the arm of the arm assembly 1013, and passes through the mounting bracket 1011. Thus, the motor shaft 1031 drives the connecting shaft 1064 and the connecting plate 1091 to rotate, and the second end 1082 of the scroll spring fixed to the connecting plate 1091 is also rotated along with the connecting plate 1091, so that the scroll spring is twisted tightly.

As shown in FIG. 9 and FIG. 10, in an embodiment of the present invention, a mounting hole 10432 is formed in the first cover 1043 of the gear box 104, and the position limiting column 10111 passes through the mounting hole 10432. A threaded hole is formed in the position limiting column 10111, and the gear box 104 is mounted to the mounting bracket 1011 via a bolt 1093 fitted within the threaded hole.

Specifically, the position limiting column 10111 passes through the position limiting notch 10921 and abuts against the first cover 1043 of the gear box 104. The mounting hole 10432 of the first cover 1043 of the gear box 104 is in one-to-one correspondence with the threaded hole of the position limiting column 10111, and the bolt 1093 passes through the mounting hole 10432 and is screwed into the threaded hole so as to fix the first cover 1043 of the gear box 104 to the mounting bracket 1011. Thus, since the first cover 1043 of the gear box 104 is fixed to the mounting bracket 1011 via the bolt 1093, it is easy to replace and maintain the scroll spring.

In addition, the present invention is not limited to this, and the first cover 1043 of the gear box 104 may be fixed with the mounting bracket 1011 via welding or other suitable manners.

A motor assembly of the vehicle step apparatus 10 is also provided in the present application. As shown in FIG. 1 to FIG. 10, the motor assembly of the vehicle step apparatus 10 includes a motor 103, a gear box 104, a worm wheel 105, a sun gear 1061, a planet carrier 1062, a planet gear 1063 and an adjusting member 107.

The motor 103 has a motor shaft 1031 configured as a worm. In other words, a helical gear is formed in at least a portion of the motor shaft 1031. The gear box 104 has a cavity 1041 therein, and at least a portion of the motor shaft 1031 is inserted into the cavity 1041. The adjusting member 107 is mounted in the gear box 104, movable in an axial direction of the motor shaft 1031 and abuts against a free end of the motor shaft 1031.

The worm wheel 105 is rotatably disposed in the cavity 1041, and includes a worm wheel body 1051 and an output shaft 1052. The worm wheel body 1051 meshes with the motor shaft 1031, and the output shaft 1052 is mounted to the worm wheel body 1051. The sun gear 1061 is fitted over the output shaft 1052.

The planet carrier 1062 is rotatably disposed in the cavity 1041 and connected with the arm assembly 1013 to drive the arm assembly 1013, further to drive the step bracket 1012 to move between the extending position and the retracting position. The planet gear 1063 is rotatably mounted to the planet carrier 1062 and meshes with the sun gear 1061.

Thus, the motor assembly of the vehicle step apparatus 10 according to embodiments of the present invention has advantages of high transmission efficiency, low noise during reversal, a compact structure, a small size, high safety, high reliability, a long working life, a low manufacture cost and so on, and is suitable to be mounted at a bottom of a vehicle, in which the bottom of the vehicle has a narrow space.

Reference throughout this specification to “an embodiment,” “some embodiments”, “an example”, “a specific example”, or “some examples”, means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. The appearances of the phrases throughout this specification are not necessarily referring to the same embodiment or example of the present invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that the above embodiments cannot be construed to limit the present invention, and changes, alternatives, and modifications can be made in the embodiments without departing from spirit, principles and scope of the present invention. 

1. Electronic device for the diagnosis of insulation loss, with respect to a ground of an energized electrical apparatus having a negative terminal and a positive terminal, through the measurement of a negative terminal insulation resistance an (RI_(minus)) Present between said negative terminal and said ground, and a positive terminal insulation resistance (RI_(plus)) present between said positive terminal and said ground, the device including: a first device terminal and a second device terminal, suitable to be connected, respectively, to the negative and positive terminals of the energized electrical apparatus; a first resistance-switch group, comprising a first sample resistance (RS_(minus)) adapted to be connected or disconnected in a controlled manner between the first device terminal and the ground by means of a first sample resistance insertion switch (S_(minus)); a first measurement circuit, arranged between the first device terminal and the ground, in parallel to the first resistance-switch group; a second resistance-switch group, comprising a second sample resistance (RS_(plus)) adapted to be connected or disconnected in a controlled manner between the second device terminal and the ground by means of a second sample resistance insertion switch (S_(plus)); a second measurement circuit, arranged between the second device terminal and the ground, in parallel to the second resistance-switch group; wherein the first measurement circuit comprises: a first detection circuit, comprising at least a first resistor (R2) and a first capacitor (C1) arranged mutually in parallel, so that at the ends of the first capacitor (C1), when the first device terminal is connected to the energized electrical apparatus, after a transient needed for the measurement to reach a first steady state, there is a first detection voltage (VC_(minus)) depending on the negative voltage (V_(minus)) of the energized electrical apparatus; the first detection circuit further comprising a first voltage meter (U_(minus)); a first charge modulation circuit, arranged in parallel to the first detection circuit, and comprising a first modulation resistance (R1) and a first modulation switch (SW1), arranged in series with the first modulation resistance (R1) and adapted to be controlled by a first driving signal (V_(SW-minus)), so that, when the first device terminal is connected to the energized electrical apparatus, the first capacitor (C1) is partially discharged and recharged, respectively, during each closing and opening period of the first modulation switch (SW1), so that the first detection voltage (VC_(minus)) oscillates between a first detection voltage maximum value (VC_(minus-MAX)) and a first detection voltage minimum value (VC_(minus-MIN)), around a first detection voltage intermediate value (VC_(minus)) representative of the negative voltage (V_(minus)) of the energized electrical apparatus; a first partition resistor (RB_(minus)) connected between the first device terminal and the first detection circuit, so that the first partition resistor (RB_(minus)) and the first detection circuit are arranged mutually in series; and wherein the second measurement circuit comprises: a second detection circuit, comprising at least a second resistor (R6) and a second capacitor (C2) arranged mutually in parallel, so that at the ends of the second capacitor (C2), when the second device terminal is connected to the energized electrical apparatus, after a transient needed for the measurement to reach a second steady state, there is a second detection voltage (VC_(plus)) depending on the positive voltage (V_(plus)) of the energized electrical apparatus; the second detection circuit further comprising a second voltage meter (U_(plus)); a second charge modulation circuit, arranged in parallel to the second detection circuit, and comprising a second modulation resistance (R5) and a second modulation switch (SW2), arranged in series with the second modulation resistance (R5) and adapted to be controlled by a second driving signal (V_(SW-plus)), so that, when the second device terminal is connected to the energized electrical apparatus, the second capacitor (C2) is partially discharged and recharged, respectively, during each closing and opening period of the second modulation switch (SW2), so that the second detection voltage (VC_(plus)) oscillates between a second detection voltage maximum value (VC_(plus-MAX)) and a second detection voltage minimum value (VC_(plus-MIN)), around a second detection voltage intermediate value (VC_(plus)) representative of the positive voltage (V_(plus)) of the energized electrical apparatus; a second partition resistor (RB_(plus)) connected between the second device terminal and the second detection circuit, so that the second partition resistor (RB_(plus)) and the second detection circuit are arranged mutually in series; wherein said first voltage meter (U_(minus)) is configured to provide the first detection voltage (VC_(minus)) under both opening and closing conditions of the first resistance-switch group switch (S_(minus)), in which conditions the first sample resistance (RS_(minus)) is connected and disconnected, respectively; and wherein said second voltage meter (U_(plus)) is configured to provide the second detection voltage (VC_(plus)) under both opening and closing conditions of the second resistance-switch group switch (S_(plus)), in which conditions the second sample resistance (RS_(plus)) is connected and disconnected, respectively.
 2. Device according to claim 1, comprising: a first device switch (M_(minus)), adapted to connect or disconnect in a controlled manner the first terminal of the device to/from the negative terminal of the energized electrical apparatus; a second device switch (M_(plus)), adapted to connect or disconnect in a controlled manner the second terminal of the device to/from the positive terminal of the energized electrical apparatus.
 3. Device according to claim 1, wherein: the first detection circuit further comprises a third resistor (R3) connected between the parallel of the first resistor (R2) and first capacitor (C1) and the ground; the second detection circuit further comprises a fourth resistor (R7) connected between the parallel of the second resistor (R6) and second capacitor (C2) and the ground.
 4. Device according to claim 1, wherein the first measurement circuit and the second measurement circuit have an identical circuit structure and have electrical parameters of corresponding resistors and capacitors respectively identical.
 5. Device according to claim 1, wherein: each of said first device switch (M_(minus)) and second device switch (M_(plus)) comprises an electromechanical switch, and wherein each of said first modulation switch (SW1) and second modulation switch (SW2) comprises a respective solid state electronic switch.
 6. Device according to claim 1, wherein each of said first voltage meter (U_(minus)) and second voltage meter (U_(plus)) comprises a respective operational amplifier.
 7. Electronic system for the diagnosis of the insulation loss of an energized electrical apparatus, comprising an electronic device according to claim 1, and further comprising a control device, wherein the control device is configured to: generate and provide to the first modulation switch (SW1) said first driving signal (V_(SW-minus)); generate and provide to the second modulation switch (SW2) said second driving signal (V_(sw-plus)); receive the first detection voltage (VC_(minus)) from the first voltage meter (U_(minus)) and the second detection voltage (VC_(plus)) from the second voltage meter (U_(plus)); determine a first value of first detection voltage (VC1 _(minus)), under condition of disconnection of the first sample resistance (RS_(minus)), and determine a second value of first detection voltage (VC2 _(minus)), under condition of connection of the first sample resistance (RS_(minus)); determine a first value of second detection voltage (VC1 _(plus)), under condition of disconnection of the second sample resistance (RS_(plus)), and determine a second value of second detection voltage (VC2 _(plus)), under condition of connection of the second sample resistance (RS_(plus)); calculate the negative terminal insulation resistance (RI_(minus)) and the positive terminal insulation resistance (RI_(plus)) of the energized electrical apparatus, on the basis of said first value of first detection voltage (VC1 _(minus)) and second value of first detection voltage (VC2 _(minus)) and/or said first value of second detection voltage (VC1 _(plus)) and second value of second detection voltage (VC2 _(plus)).
 8. System according to claim 7, further configured to: determine the first value of first detection voltage (VC1 _(minus)), on the basis of said first detection voltage maximum value (VC1 _(minus-MAX)) and first detection voltage minimum value (VC1 _(minus-MIN)), in conditions of disconnection of the first sample resistance (RS_(minus)), and determine the second value of first detection voltage (VC2 _(minus)), on the basis of said first detection voltage maximum value (VC2 _(minus-MAX)) and first detection voltage minimum value (V2C_(minus-MIN)), in condition of connection of the first sample resistance (RS_(minus)); determine the first value of second detection voltage (VC1 _(plus)), on the basis of said second detection voltage maximum value (VC1 _(plus-MAX)) and second detection voltage minimum value (VC1 _(plus-MIN)), in conditions of disconnection of the second sample resistance (RS_(plus)), and determine the second value of second detection voltage (VC2 _(plus)), on the basis of said second detection voltage maximum value (VC2 _(plus-MAX)) and second detection voltage minimum value (V2C_(plus-MIN)), in conditions of connection of the second sample resistance (RS_(plus)).
 9. System according to claim 7, wherein: said first driving signal (V_(SW-minus)) is a pulse signal having a first frequency, wherein the presence and absence of the pulse control the closing and opening, or the opening and closing, of the first modulation switch (SW1), and wherein the pulse duration with respect to the period associated with the first frequency defines a first close-open duty-cycle (DC1); said second driving signal (V_(SW-plus)) is a pulse signal having a second frequency, wherein the presence and absence of the pulse control the closing and opening, or the opening and closing, of the second modulation switch (SW2), and wherein the pulse duration with respect to the period associated with the second frequency defines a second close-open duty-cycle (DC2).
 10. System according to claim 9, wherein the control device is further configured to dynamically adjust, during the measurement, one or any combination of the following parameters: first frequency of the first driving signal (V_(SW-minus)); second frequency of the second driving signal (V_(SW-plus)); first close-open duty-cycle (DC1); second close-open duty-cycle (DC2).
 11. System according to claim 9, wherein: the first and the second driving signal (V_(SW-minus), V_(SW-plus)) are periodic signals of Pulse Width Modulation (PWM) type; the first and the second driving frequency are equal to each other; the first closing-opening duty-cycle (DC1) and the second close-open duty-cycle (DC2) are equal to each other; the first driving signal (V_(SW-minus)) and the second driving signal (V_(SW-plus)) are equal or complementary to each other.
 12. (canceled)
 13. Method for measuring a negative terminal insulation resistance (RI_(minus)), present between a negative terminal and the ground of an energized electrical apparatus, and a positive terminal insulation resistance (RI_(plus)), present between a positive terminal and the ground of the energized electrical apparatus, the method comprising the steps of: connecting a first measurement circuit between said negative terminal and ground to detect a first value (VC1 _(minus)), of a first detection voltage (VC_(minus)), depending on the negative voltage (V_(minus)) of the energized electrical apparatus; connecting a second measurement circuit between said positive terminal and ground to detect a first value (VC1 _(plus)) of a second detection voltage (VC_(plus)), depending on the positive voltage (V_(plus)) of the energized electrical apparatus; alternatively, connecting a first sample resistance (RS_(minus)) in parallel to the first measurement circuit between said negative terminal and ground, or connecting a second sample resistance (RS_(plus)) in parallel to the second measurement circuit between said positive terminal and ground; under said connection condition of connection of one of the first sample resistance (RS_(minus)) and the second sample resistance (RS_(plus)), detecting a second value (VC2 _(minus)) of the first detection voltage (VC_(minus)), and detecting a second value (VC2 _(plus)) of the second detection voltage (VC_(plus)); calculating the negative terminal insulation resistance (RI_(minus)) and the positive terminal insulation resistance (RI_(plus)) of the energized electrical apparatus, on the basis of said first value of first detection voltage (VC1 _(minus)), second value of first detection voltage (VC2 _(minus)), first value of second detection voltage (VC1 _(plus)) and second value of second detection voltage (VC2 _(plus)); wherein said step of detecting a first value of first detection voltage (VC1 _(minus)) comprises modulating the first detection voltage (VC_(minus)), by means of a modulation signal, detecting the modulated first detection voltage (VC_(minus)), and determining the first value of first detection voltage (VC1 _(minus)) on the basis of the modulated first detection voltage (VC_(minus)); wherein said step of detecting a first value of second detection voltage (VC1 _(plus)) comprises modulating the second detection voltage (VC_(plus)) by of a modulation signal, detecting the modulated second detection voltage (VC_(plus)), and determining the first value of second detection voltage (VC1 _(plus)) on the basis of the modulated second detection voltage (VC_(plus)); wherein said step of detecting a second value of first detection voltage (VC2 _(minus)) comprises: modulating again the first detection voltage (VC_(minus)) by of the modulation signal, while said first sample resistance (RS_(minus)) or second sample resistance (RS_(plus)) is connected; detecting again the modulated first detection voltage (VC_(minus)); determining the second value of first detection voltage (VC2 _(minus)) on the basis of the modulated first detection voltage (VC_(minus)), detected while said first sample resistance (RS_(minus)) or second sample resistance (RS_(plus)) is connected; and wherein said step of detecting a second value of second detection voltage (VC2 _(plus)) comprises: modulating again the second detection voltage (VC_(plus)) by of the modulation signal, while said first sample resistance (RS_(minus)) or second sample resistance (RS_(plus)) is connected; detecting again the modulated second detection voltage (VC_(plus)); determining the second value of second detection voltage (VC2 _(plus)) on the basis of the modulated second detection voltage (VC_(plus)), while said first sample resistance (RS_(minus)) or second sample resistance (RS_(plus)) is connected.
 14. Method according to claim 13, including, prior to the step of connecting the first or second sample resistance, the further step of comparing the first value of first detection voltage (VC1 _(minus)) and the first value of second detection voltage (VC_(plus)); and wherein said step of connecting a first sample resistance (RS_(minus)) or a second sample resistance (RS_(plus)) comprises: connecting the first sample resistance (RS_(minus)), keeping the second sample resistance (RS_(plus)) disconnected, if the first detection voltage (VC_(minus)), is greater than the second detection voltage (VC_(plus)); connecting the second sample resistance (RS_(plus)), keeping the first sample resistance (RS_(minus)) disconnected, if the first detection voltage (VC_(minus)) is less than the second detection voltage (VC_(plus)).
 15. Method according to claim 13, wherein: the step of modulating the first detection voltage (VC_(minus)) comprises modulating the first detection voltage (VC_(minus)) so that it oscillates between a first detection voltage maximum value (VC1 _(minus-MAX)) and a first detection voltage minimum value (VC1 _(minus-MIN)); the step of modulating again the first detection voltage (VC_(minus)) comprises modulating again the first detection voltage (VC_(minus)) so that it oscillates between a new first detection voltage maximum value (VC2 _(minus-MAX)) and a new first detection voltage minimum value (VC2 _(minus-MIN)); the step of modulating the second detection voltage (VC_(plus)) comprises modulating the second detection voltage (VC_(plus)) so that it oscillates between a of second detection voltage maximum value (VC1 _(plus-MAX)) and a of second detection voltage minimum value (VC1 _(plus-MIN)); the step of modulating again the second detection voltage (VC_(plus)) comprises modulating the second detection voltage (VC_(plus)) so that it oscillates between a new second detection voltage maximum value (VC2 _(plus-MAX)) and a new second detection voltage minimum value (VC2 _(plus-MIN)).
 16. Method according to claim 15, wherein: the step of detecting the first detection voltage comprises measuring said first detection voltage maximum value (VC1 _(minus-MAX)) and first detection voltage minimum value (VC1 _(minus-MIN)); and the step of determining a first value of first detection voltage comprises determining the first value of first detection voltage (VC1 _(minus)) on the basis of said first detection voltage maximum value (VC1 _(minus-MAX)) and first detection voltage minimum value (VC1 _(minus-MIN)); the step of detecting again the first detection voltage comprises measuring again the first detection voltage maximum value (VC2 _(minus-MAX)) and the first detection voltage minimum value (VC2 _(minus-MIN)), while the first sample resistance (RS_(minus)) or the second sample resistance (RS_(plus)) is connected; and the step of determining a second value of first detection voltage comprises determining the second value of first detection voltage (VC2 _(minus)) on the basis of said first detection voltage maximum value (VC2 _(minus-MAX)) and first detection voltage minimum value (VC2 _(minus-MIN)), detected while the first sample resistance (RS_(minus)) or the second sample resistance (RS_(plus)) is connected; the step of detecting the second detection voltage comprises measuring said second detection voltage maximum value (VC1 _(plus-MAX)) and second detection voltage minimum value (VC1 _(plus-MIN)); and the step of determining a first value of second detection voltage comprises determining the first value of second detection voltage (VC1 _(plus)) on the basis of said second detection voltage maximum value (VC1 _(plus-MAX)) and second detection voltage minimum value (VC1 _(plus-MIN)); the step of detecting again the second detection voltage comprises measuring again the second detection voltage maximum value (VC2 _(plus-MAX)) and the second detection voltage minimum value (VC2 _(plus-MIN)), while the first sample resistance (RS_(minus)) or the second sample resistance (RS_(plus)) is connected; and the step of determining a second value of second detection voltage comprises determining the second value of second detection voltage (VC2 _(plus)) on the basis of said second detection voltage maximum value (VC2 _(plus-MAX)) and second detection voltage minimum value (VC2 _(plus-MIN)), detected while the first sample resistance (RS_(minus)) or the second sample resistance (RS_(plus)) is connected.
 17. Method for diagnosing an insulation loss of an energized electrical apparatus, comprising: measuring a negative terminal insulation resistance (RI_(minus)), present between a negative terminal and the ground of an energized electrical apparatus, and a positive terminal insulation resistance (RI_(plus)), present between a positive terminal and the ground of the energized electrical apparatus; diagnosing the insulation loss of the energized electrical apparatus on the basis of the negative terminal insulation resistance (RI_(minus)) measured and of the positive terminal insulation resistance (RI_(plus)) measured, wherein said measuring step is performed by a method according to claim
 13. 18. Method of self-diagnosis of an electronic device for diagnosing the insulation loss of an energized electrical apparatus, the device being according to claim 1, the method comprising the steps of: performing a diagnosis of the functioning of the first resistance-switch group (RS_(minus), S_(minus)) and of the second resistance-switch group (RS_(plus), S_(plus)) of the device, on the basis of measurements of the first (VC_(minus)) and of the second detection voltage (VC_(plus)), carried out by the device under conditions in which the first sample resistance input switch (S_(minus)) and the second sample resistance input switch (S_(plus)) are in a plurality of conditions, respectively, belonging to the following set of conditions: open, open; closed, open; open, closed; closed, closed; performing a consistency test of the measurement made by the device on the basis of the first detection voltage (VC_(minus)) and the second detection voltage (VC_(plus)), as measured by the device, and of the battery voltage (VB), the value of which is available regardless of the measurements of the device; checking the presence and measuring the amplitude of a first oscillation (ΔVC_(minus)) of the first detection voltage (VC_(minus)) around its steady state value, while the first modulation switch (SW1) switches between opening and closing, and further checking the presence and measuring the amplitude of a second oscillation (ΔVC_(plus)) of the second detection voltage (VC_(plus)) around its steady state value, while the second modulation switch (SW2) switches between opening and closing; performing a diagnosis of the functioning of the first measurement circuit and of the second measurement circuit of the device, on the basis of measurements of the first detection voltage (VC_(minus)), the second detection voltage (VC_(plus)), the amplitude of the first oscillation (ΔVC_(minus)) and the amplitude of the second oscillation (ΔVC_(plus)).
 19. Self-diagnosis method according to claim 18, wherein the method comprises, before the step of performing a diagnosis of the functioning of the first resistance-switch group, the further step of: performing a diagnosis of the functioning of the device switches (M_(minus), M_(plus)), on the basis of the first detection voltage (VC_(minus)) and of the second detection voltage (VC_(plus)), measured by the device in condition of closed device switches (M_(minus), M_(plus)).
 20. Self-diagnosis method according to claim 18, wherein the step of performing a diagnosis of the functioning of the resistance-switch groups comprises measuring the first (VC_(minus)) and the second detection voltage (VC_(plus)), under conditions in which the first sample resistance input switch (S_(minus)) and the second sample resistance input switch (S_(plus)) are respectively set in the following conditions: open, open; closed, open; open, closed; closed, closed.
 21. Self-diagnosis method according to claim 20, wherein the step of performing a diagnosis of the functioning of the resistance-switch groups comprises: a first test comprising opening the first sample resistance input switch (S_(minus)) and the second sample resistance input switch (S_(plus)), measuring the first (VC_(minus)) and the second detection voltage (VC_(plus)), comparing the absolute value of the difference between said first and second detection voltage with a first threshold (THR0), and determining a positive result of the first test if said absolute value of the difference is less than the first threshold (THR0); a second test comprising closing the first sample resistance input switch (S_(minus)) and opening the second sample resistance input switch (S_(plus)), measuring the first (VC_(minus)) and the second detection voltage (VC_(plus)), comparing the difference between the second detection voltage (VC_(plus)) and the first detection voltage (VC_(minus)) with a second threshold (THR1), and determining a positive result of the second test if said difference is greater than the second threshold (THR1); a third test comprising opening the first sample resistance input switch (S_(minus)) and closing the second sample resistance input switch (S_(plus)), measuring the first (VC_(minus)) and the second detection voltage (VC_(plus)), comparing the difference between the first detection voltage (VC_(minus)) and the second detection voltage (VC_(plus)) with said second threshold (THR1), and determining a positive result of the third test if said difference is greater than the second threshold (THR1); a fourth test comprising closing the first sample resistance input switch (S_(minus)) and the second sample resistance input switch (S_(plus)), measuring the first (VC_(minus)) and the second detection voltage (VC_(plus)), comparing the absolute value of the difference between said first and second detection voltage with a third threshold (THR2), and determining a positive result of the fourth test if said absolute value of the difference is less than the third threshold (THR2); diagnosing a correct functioning of the resistance-switch groups if said first, second, third and fourth tests all provide a positive result.
 22. Method according to claim 21, wherein said first test further comprises comparing the absolute value of the difference between said first and second detection voltage with a calibration threshold (THRc) to determine a first or a second value for the second threshold (THR1) and a first or a second value for the third threshold (THR2), depending on whether said absolute value of the difference is higher or lower than the calibration threshold (THRc).
 23. Self-diagnosis method according to claim 18, wherein the step of performing a consistency test of the measurement made by the device comprises: calculating the sum of the first detection voltage (VC_(minus)), and of the second detection voltage (VC_(plus)); storing the difference between the positive (V_(plus)) and negative (V_(minus)) voltage of the battery, on the basis of the battery voltage (V_(B)) that known is irrespective of the measurements of the device; calculating a comparison value, by weighing said difference between the battery voltages with a factor (A) dependent on the electrical parameters of the device; determining a positive result of the consistency test if said sum of the first detection voltage (VC_(minus)) and the second detection voltage (VC_(plus)) differs from said comparison value by less than a predefined amount.
 24. Self-diagnosis method according to claim 18, wherein the step of checking the presence and measuring the amplitude of a first and of a second oscillation comprises: switching the first modulation switch (SW1) between opening and closing, by the first driving signal; measuring the first detection voltage maximum value (VC_(minus-MAX)) and the first detection voltage minimum value (VC_(minus-MIN)), and calculating the difference between said maximum value and minimum value of first detection voltage to determine the first oscillation amplitude (ΔVC_(minus)); switching the second modulation switch (SW2) between opening and closing, by the second driving signal; measuring the of second detection voltage maximum value (VC_(plus-MAX)) and the second detection voltage minimum value (VC_(plus-MIN)), and calculating the difference between said maximum value and minimum value of second detection voltage to determine the second oscillation amplitude (ΔVC_(plus)); checking that the first oscillation amplitude (ΔVC_(minus)) remains within a predefined range of acceptable values, dependent on the first detection voltage (VC_(minus)); checking that the second oscillation amplitude (ΔVC_(plus)) remains within a predefined range of acceptable values, dependent on the second detection voltage (VC_(plus)).
 25. Self-diagnosis method according to claim 18, wherein the step of performing a diagnosis of the functioning of the first and second measurement circuit comprises: identifying a first group of possible faults of the first measurement circuit if the first detection voltage (VC_(minus)) is lower than a low threshold (VTHRL); identifying a second group of possible faults of the first measurement circuit if the first detection voltage (VC_(minus)) is higher than a first high threshold (VTHR-H1); identifying a third group of possible faults of the first measurement circuit if the amplitude of the first oscillation (ΔVC_(minus)) is lower than a low threshold (VTHRL); identifying a fourth group of possible faults of the first measurement circuit if the amplitude of the first oscillation (ΔVC_(minus)) is higher than a second high threshold (VTHR-H2); identifying a first group of possible faults of the second measurement circuit if the second detection voltage (VCplus) is lower than a low threshold (VTHRL); identifying a second group of possible faults of the second measurement circuit if the second detection voltage (VCplus) is higher than a third high threshold (VTHR-H3); identifying a third group of possible faults of the second measurement circuit if the amplitude of the second oscillation (ΔVC_(plus)) is lower than a low threshold (VTHRL); identifying a fourth group of possible faults of the second measurement circuit if the amplitude of the second oscillation (ΔVC_(plus)) is higher than a fourth high threshold (VTHR-H4); determining a correct functioning of the first and the second measurement circuit if, as a result of the preceding steps of identifying, no fault is identified. 